Non-impact printing methods are known in which visual information is printed on moving paper webs or other materials as desired using a device which directs coloring matter towards the web surface under the influence of electrical signal control circuitry. Non-impact printing devices include the well known so-called jet printers, such as disclosed in U.S. Pat. Nos. 3,060,429 of C. R. Winston, 3,577,198 of D. R. Beam, 3,416,153 of C. H. Hertz et al, 3,562,757 of V. E. Bischoff, 3,769,624 of C. H. Lee et al, 3,769,627 of J. J. Stone and others. In addition electrokinetic methods are known in which the printing head is positioned in virtual contact with the web surface, such as is disclosed in U.S. Pat. No. 3,750,564 of H. Bettin.
The jet printing mechanisms disclosed in the aforementioned U.S. patents generally disclose the generation of a stream of ink droplets at least portion of which are electrostatically charged. Signal controlled deflector means are used to cause droplets to contact the moving web surface whereas droplets not forming part of the information are prevented from contacting the said surface by the use of a catcher or the like from which the unused droplets of ink are returned to the reservoir. The disclosure of Bettin in U.S. Pat. No. 3,750,564 and J. P. Arndt in U.S. Pat. No. 3,832,579 each reveal non-impact printing methods in which a signal is employed to form droplets of finite quantity of recording material without the need for return of excess ink to the system reservoir.
Generally prior art non-impact printing methods produce visible printed deposits on moving webs such as paper at high speed. Such systems are generally of limited resolution and produce printed deposits of relatively low density which consequently are normally inadequate for subsequent recognition by for instance Optical Character Recognition or Magnetic Image Character Recognition means for further information processing, as is readily attainable with information printed by contact processes such as lithography, letterpress and the like.